DESCRIPTION: (Adapted from the applicant's proposal) Cells exiting mitosis undergo a series of dramatic events: the mitotic spindle breaks down, p34CD28/cyclin B mitotic kinase activity diminishes, chromosomes decondense and reconfigure, cytokinesis occurs, and the cellular machinery is reset for entry into the ensuing G1 phase. The molecular mechanisms that regulate and coordinate these essential processes are poorly understood. This project seeks to identify and characterize genes that execute or regulate cellular activities at this critical stage of the cell cycle. A genetic method and accompanying molecular approaches will investigate the role that CDC14, a Saccharomyces cerevisiae cell-division cycle gene required for completion of telophase, play in exit from mitosis. The particular function of CDC14 in the telophase-to-G1 transition is unknown. To investigate the pathway in which CDC14 acts, dominant extragenic suppressor of temperature-sensitive alleles of cdc14 will be isolated. Dominant extragenic suppressors of cdc14 may identify genes whose products physically associate with CDC14 and are thus themselves important for late mitototic events. Genes which regulate expression of CDC14, or which act downstream of CDC14, may also be identified by this approach. Cloning the suppressor genes, along with cytological and additional genetic analyses of suppressor mutants, will further define the roles of these newly identified genes in exit from mitosis. CDC14 encodes a putative protein tyrosine phosphatase. Protein tyrosine phosphatases are important in cellular differentiation, development, and cancer, but their precise functions in signaling pathways that control these processes are not well understood. If protein dephosphorylation led by CDC14 regulates exit from mitosis, genes identified as suppressors of cdc14 may be components of such a signaling pathway. An additional specific aim of this proposal is to purify CDC14 protein produced in E. coli, for use in generating polyclonal antibodies against CDC14. These antibodies will be used in future experiments designed to identify CDC14 interactions with other polypeptides. In the current proposal, western blot analysis using anti-CDC14 antibodies will ascertain whether a subset of the cdc14-suppressor mutants may identify genes whose encoded proteins interact with CDC14.